Raising the minimum legal drinking age (MLDA) from 18 to 21 years has reduced alcohol-related traffic crash fatalities from 6 to 30%, despite inconsistent state laws, limited implementation and modest enforcement (Fell et al., 2007; Shults et al., 2001; Wagenaar, 1983; Wagenaar and Toomey, 2002).
The MLDA is one of the most widely studied alcohol prevention policies. A recent systematic review by the Centers for Disease Control and Preventions Task Force on Community Preventive Services identified 46 studies meeting their inclusion criteria of the effects of the MLDA on variety of alcohol-related traffic crash indicators. All of these studies have consistently shown reductions in alcohol-related traffic crashes with increases in the MLDA, with effects ranging from 6% to 30%. A recent study (Fell et al., 2007) contributes to the evidence of the effectiveness of this law, showing a national 11.7% reduction in the ratio of underage drinking drivers to underage non-drinking drivers in fatal crashes following the increases in the MLDA from 18 to 21 years. These results are confirmed by a recent evaluation of New Zealands reduction in drinking age from 21 to 18 in 1999, where the youth crash rate increased 12% (Kyrpi et al., 2005). The important health and safety benefits of the age-21 MLDA are now very well established in the scientific literature, documented in an exhaustive review of 132 studies by Wagenaar and Toomey (2002). Follow-up analyses by Carpenter et al. (2007) confirm earlier results of OMalley and Wagenaar (1991) that a key mechanism of effect of the higher legal drinking age is that the law significantly reduces both the proportion of teens who drink (30-day prevalence) and the proportion who drink heavily (5 or more drinks at a time).